Ultrathin silver films on Ni(111)

摘要

The growth and atomic structure of ultrathin silver films on Ni(111) was investigated by low-energy electron microscopy and diffraction (LEEM/LEED) as well as intensity-voltage [I(V)]-LEEM in the growth temperature range between 470 and 850 K. We find that silver grows in a Stranski-Krastanov mode with a two monolayer thin wetting layer which takes on a p(7 × 7) reconstruction at temperatures lower than 700 K and a ((52)~(1/2) × (52)~(1/2))R13.9° reconstruction at higher temperatures. The occurrence of the two distinct reconstructions is shown to have profound implications for the growth characteristics of films exhibiting thicknesses of one and two monolayers. The nanoscale I(V) characteristics of the films were analyzed by means of multiple-scattering calculations based on dynamical LEED theory. Furthermore, the vertical interatomic spacing at the interface between the Ag film and the Ni substrate was determined to (2.8 ±0.1) A for all film thicknesses (<13 ML) while the uppermost silver layer relaxes by about (4± 1)% toward the crystal.